Heltec Wireless Stick Lite V3 uses spi(1) to access SX1262, conflicting with Flash/RAM access

[MrSniffer]

My application does ocassional reads and write to the SOC flash memory and it appears the RadioLib default uses the same SPI controller of the esp32s3. It exhibits errors like -707 ERR_SPI_CMD_FAILED on radio.transmits, etc. I attempt to force the use of SPI2, as follows:

SPIClass spi(2); // 1 accesses BOTH sx1262 & flash, HSPI == 2 does not connect to SX1262
SPISettings spiSettings(4000000, MSBFIRST, SPI_MODE0);
SX1262 radio = new Module(8, 14, 12, 13, spi, spiSettings);

and then:

spi.begin(9, 11, 10, -1); //SCK, MISO, MOSI, SS
int state = radio.begin(0.01f*parms->freq, etc. etc....

using spi(1) exhibits the bus errors as described. using spi(2) gives a state = -2, e.g the SX1262 is not found at all by radio.begin.

I am using these platformio.ini values:
`[env]
framework = arduino
platform = https://github.com/platformio/platform-espressif32.git#v6.4.0
platform_packages = framework-arduinoespressif32@^3.1.0
lib_deps = jgromes/RadioLib@^7.4.0

[env:WS_SX1262]
board = heltec_wifi_lora_32_V3
board_upload.maximum_size = 1310720
board_upload.maximum_data_size = 327680
board_build.target = esp32s3
board_build.mcu = esp32s3
board_build.variant = heltec_WIFI_LoRa_32_V3
;board_build.variant = heltec_wireless_stick_lite_v3 THESE ARE WRONG PIN defines!
board_build.flash_size = 8MB
board_upload.flash_size = 8MB
board_build.partitions = config_8MB.csv
board_build.f_flash = 80000000L`

[jgromes]

If the Flash memory shares the same SPI pins as the radio, then changing the SPI controller will not help as it still would need to access those same pins.

I don't know what your overall environment looks like, but if you have multiple threads accessing the SPI then you have to make sure those accesses are thread-safe. The SPI library for ESP32 Arduino core has support for that, but I don't know if it is enabled by default or not.

[MrSniffer]

The esp32s3 has four bus controllers. I understand that the flash memory on the Heltec Wireless Stick Lite V3 (WSL V3) is an embedded 8 MB Quad SPI flash integrated within the ESP32-S3FN8 SoC package. It is accessed internally by the ESP32-S3's dedicated SPI controller (specifically, the MSPI module, which handles high-speed access to embedded or external memory via SPI0/SPI1 interfaces configured for cache and execution). No external bus or user-accessible GPIO pins are involved in flash memory access, as the connection is entirely internal to the chip.

I map spi(2) to the LoRa pin GPIOs as below but then radioLib doesn't see the SX1262 when I radio.begin. My initialization of the SX1262 instance is:

    #define HSPI 2     // skip over SPI0/1
    SPIClass spi(HSPI);     // 0 or 1 accesses the sx1262, HSPI == 2 or 3 does not.
    SPISettings spiSettings(4000000, MSBFIRST, SPI_MODE0);
    SX1262 radio = new Module(8, 14, 12, 13, spi, spiSettings);

I do the following just before radio.begin(freq, ......)

#define LORA_SCK 9
#define LORA_MISO 11
#define LORA_MOSI 10 
#define LORA_NSS 8
  // --- CRITICAL FIX: MANUAL GPIO MATRIX PROGRAMMING ---
  // The Arduino core maps SPIClass(2) to the hardware peripheral SPI3 on the ESP32-S3.
  // We must explicitly connect the custom GPIOs to the SPI3 signals.
  
  // 1. SCK (Clock) - Output from ESP32, linked to SPI3_CLK_OUT_IDX
  gpio_set_direction((gpio_num_t)LORA_SCK, GPIO_MODE_OUTPUT);
  gpio_matrix_out((gpio_num_t)LORA_SCK, SPI3_CLK_OUT_IDX, false, false);
  
  // 2. MOSI (Master Out) - Output from ESP32, linked to SPI3_D_OUT_IDX
  gpio_set_direction((gpio_num_t)LORA_MOSI, GPIO_MODE_OUTPUT);
  gpio_matrix_out((gpio_num_t)LORA_MOSI, SPI3_D_OUT_IDX, false, false); 
  
  // 3. MISO (Master In) - Input to ESP32, linked to SPI3_Q_IN_IDX
  gpio_set_direction((gpio_num_t)LORA_MISO, GPIO_MODE_INPUT);
  gpio_matrix_in((gpio_num_t)LORA_MISO, SPI3_Q_IN_IDX, false);

  gpio_set_direction((gpio_num_t)LORA_NSS, GPIO_MODE_OUTPUT);
  gpio_matrix_out((gpio_num_t)LORA_NSS, SPI3_CS0_OUT_IDX, false, false); 
  
  // 4. Initialize the SPI bus.
  // This uses the pins defined above and starts the clock.
  spi.begin(); 
  // --- END OF GPIO MATRIX ---

But then I don't see the chip. Using spi(1) finds the SX1262 but seems to conflict with flash accessing.

int state = radio.begin(freq, ....); returns -2

[MrSniffer]

I am closing this because I believe the failure observed was not due to the SX1262 and Flash being on the same bus. I think it was caused by code which toggled NSS/CS that messed up the SPI command sequencing.